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Troxler Models 3223 and 3333 depth-moisture neutron probes were modified to allow external control and data recording. Complete procedures are presented including a materials list, step-by-step instructions, and a circuit design. The procedure taken is low cost, effective, easy to complete, and greatly increases the functionality of older neutron probes. This modification provides a good option for researchers wishing to upgrade existing instruments or in some cases, return an out-of-order meter to service.